Is there any way to compare the content of one dimension with a content from an other language dimension?
When no:
How I can delete/reset a language dimension of a site? Because than I can create the new language dimension with a copy of the origin dimension.
I think you cant’t compare 2 dimensions on an easy way.
If it’s ok to delete the dimension, than you should delete the language configuration in your settings.yaml. On command line execute ./flow node:repair. Now add the language configuration back.